Hand operated impact wrench



NOV. 17, 1964 DURKEE 3,157,074

HAND OPERATED IMPACT WRENCH Filed June 27, 1962 l 3 INVENTOR.

2o LLOYD M. DURKEE BY I8 5 'Z Y ,Js M

ATTORNEYS United States Patent Ofilice 3,157,074 HAND OPERATED IMPACT WRENCH Lloyd M. Durkee, 395 N. Eim Sh, Prinevilie, Oreg. Filed June 27, 1962, Ser. No. 265,650 8 Claims. ((31. til-52.3)

This invention relates to a hand operated impact wrench for tightening or loosening nuts on bolts or threaded rods and tightening or loosening bolts in screw threaded holes.

The object of this invention is to provide an effective hand operated impact wrench which can be manufactured at a low cost and which will perform the same tasks on such jobs as wheel bolts or nuts, body or frame bolts, cylinder head bolts, etc. as the present known but more expensive electrical and pneumatic impact wrenches.

Another object of the present invention is to provide a hand operated impact wrench which can use the various wrench sockets at present available for different sizes of nuts and bolts and also can use extension shafts when the latter are needed.

A further object of the present invention is to provide a hand operated impact wrench which includes a novel arrangement of a fixed dual hammer and a floating dual anvil as the means for creating the impact or shock, which is necessary for the operation of the wrench when manually used in the intended manner.

till other objects, advantages and improvements will become apparent from the following specification, taken in connection with the accompanying drawing, in which:

FIGURE 1 is a side elevational view of the hand operated impact wrench according to the present invention, with certain parts being shown in section;

FIGURE 2 is a transverse sectional view, taken on the section line 2-2 of FIGURE 1 and looking in the direction of the arrows, and showing the novel arrangement of the fixed dual hammer and the floating dual anvil; and,

FIGURE 3 is a side elevational view, also with certain parts shown in section, of a modified form of the hand operated impact wrench according to the present invention.

Referring now to the drawings in detail and to FIG- URE 1 in particular, the operating handle has a hand grip 11 an integral offset crank 11, and a shank12, which has an axial bore 13 therethrough and which is co-axial with respect to the hand grip 1t). Radially positioned arms 15-15 are integral with the shank 12, or secured thereto by welding, and carry arcuately shaped hammer heads 18-18 at their outer ends. These hammer heads are sector shaped and have sides disposed along radial planes through the axis of the shank 12, that is through the axis of rotation. Also the hammer heads are ofiset outwardly from the plane of the hammer arms.

The anvil is comprised by oppositely disposed arms 111-19 having arcuately shaped anvil members 26-21) at their outer ends, which latter are disposed intermediate the hammer heads 18-18. The anvil arms are mounted on a central shaft 21, being integrally formed therewith or secured thereto by Welding. These anvil members are also of sector shape and have sides disposed along radial planes through the axis of the central shaft 21, which is also the axis of rotation. Further, the anvil members are thicker than the arms 19-19, and ofiset from the latter both inwardly and outwardly, and their areuate tops are disposed in the same cylindrical surface as the arcuate tops of said hammer heads 18-18. The shaft 21 extends on both sides of the anvil arm 19-19 and on one side is received in close bearing engagement in the axial bore 13 in the shank 12. This close fit of the shaft 21 in the bore 13 maintains the hammer heads 18-18 and the anvil members -20 in exact align- 3,.l57,d74 Fatented Nov. 17, 1964 ment transversely of the shaft 21. Adjacent its end disposed within the axial bore 13 of the shank 12, the shaft 21 is formed with an annular groove 22 and a radially positioned set screw 14 extends through a suitable screw threaded hole in the shank 12 and is received within this groove. This form of connection allows the shank 12 to rotate freely with respect to the shaft 21 but prevents any relative axial displacement of these two elements.

The other end of the shaft 21 is formed as a square section 21a. The conventional wrench sockets 30 are closed at one end at S-da and square holes 31 are formed through the closed ends. These square holes receive the square end 21a of the shaft 21. A hole 27 is formed in one face or" the square end 21a of the shaft and extends inwardly beyond the center of the square. In this hole there is received a ball detent 29, which is biased outwardly by a coiled compression spring 23. This detent engages in a suitable recess which is formed as a segment of a spherical surface in one face of the square hole 31 in the end wall of the socket. This detent forms a quick detachable connection between the socket 311 and the shaft 21.

The interiors of the wrench sockets 30 are formed as regular prismatic surfaces at 32, of four, six or eight sides. The sockets are thus adapted to be received over nuts 33 on bolts 34, which may be wheel bolts on a wheel flange 35.

The modification according to FIGURE 3 differs from that according to FIGURE 1 in the position of the free running connection between the crank 11 and the hammer arms 1 3-19. The hammer heads 18-18 and the anvil members 219-211 here have the same shapes as in the previous modification. The hammer arms 19-19 are here integrally formed with, or welded to, a hub 24 on one side, a concentrically positioned spacer boss 26 being similarly united to the hub on the other side. An axial bore 25 extends through the spacer boss 26 and for most of the length of the hub 24. The hammer arms 15-15 are integrally formed with a centrally positioned and outwardly extending shaft 16, which is received in close bearing engagement in the bore 25 through the boss 26 and the hub 24-. The hand grip 10 and the centrally positioned shaft 16 are axially aligned, their common axis being the axis of rotation of the hammer heads 18-18, and the crank 11 is eccentrically positioned with respect to this axis. Adjacent its outer end the shaft 16 is formed with an annular groove 17 therein and a radially positioned set screw 14- extends through a suitable screw threaded hole in the hub 2 and is received within this groove. This form of connection likewise allows the shaft 16 to rotate freely with respect to the hub 24 but prevents any relative axial displacement of these two elements. At its outer end the hub 24 is formed with a reduced square section 24a for the reception of the wrench sockets 31 A hole 27 is also formed in one face of the square section 24a of the hub and extends inwardly beyond the center of the square for reception of the ball detent 29 and its biasing spring 28.

In the use of the hand operated impact wrench, the proper size wrench socket 319 is selected and placed on either the square end 21a of the shaft 21 or the square end 24a of the hub 24, where it is held in position by the ball detent 29. The wrench socket 311 is then placed over the nut 33 on a wheel bolt 34, for example, as shown in FIGURE 1. The crank 11 is then rotated in the reverse direction to that shown by the arrows in FTGURE 2, to increase the angle between the arms 19-19, which carry the anvil members 20-20, and the arms 15-15, which carry the hammer heads 18-18. The crank 11 is then rotated with rapid angular movement in the direction shown by the arrows in FEGURE 2. The hammer heads 18-18 acquire kinetic energy, which is a function of both their mass and the square of their angular velocity. Upon impact of the hammer heads 18-18 with the anvil members 2tl-2tl, the momentum of the former is transferred to the latter in a sharp striking blow. The impact then received by the anvil members 2tl2tl is transferred through the anvil arms 19-l9 and the shaft 21 or the hub 24 to the wrench socket and the nut 31. This impact is sufficient to loosen extra tight nuts 33, or bolts, or to tighten nuts 33, or bolts, where an impact wrench is needed. The direction in which the crank 11 will be turned to first back off the hammer heads its-18 from the anvil members 20-2 9 and then the opposite direction in which it will be turned to impart the striking blow to the anvil members, will be determined by whether the threads on the wheel bolt 34 are right or left handed and whether the nuts 33 are to be loosened or tightened.

Having now fully described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. An impact wrench comprised by a first rotatable member, a crank on said first rotatable member, a second concentrically positioned rotatable member adapted to receive a wrench socket, a free running connection between said rotatable members, a first pair of arms on said first rotatable member, sector shaped hammer heads mounted on the outer ends of said arms, a second pair of arms on said second rotatable member, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of said hammer heads, and being positioned intermediate the hammer heads and also aligned with the latter transversely of the axis of said rotatable members.

2. An impact wrench comprised by a shank, a crank on said shank, a shaft adapted to receive a wrench socket at one end concentrically disposed with respect to said shank, a free running connection between said shank and said shaft, a first pair of oppositely disposed arms on said shank, sector shaped hammer heads mounted on the outer ends of said arms, a second pair of oppositely disposed arms in said shaft, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of the hammer heads, and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shank and the shaft.

3. An impact wrench comprised by a shank having an axial bore therein, a crank on said shank, a shaft adapted to receive a wrench socket on one end and rotatably received in the axial bore in the shank at the other end, a first pair of oppositely disposed arms on said shank, sector shaped hammer-heads mounted on the outer ends of said arms, a second pair of oppositely disposed arms on said shaft, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of said hammer heads and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shank and the shaft.

4. An impact wrench comprised by a shank having an axial bore therein, a crank on said shank, a shaft adapted to receive a wrench socket at one end, having an annular groove therein adajacent the other end and rotatably received at the latter end in the axial bore in the shank, a set screw extending through the Wall of the shank and received in the annular groove in the shaft, a first pair of oppositely disposed arms on said shank, sector shaped hammer heads mounted on the outer ends of said arms, a second pair of oppositely disposed arms on said shaft and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of said hammer i heads, and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shank and the shaft.

5. An impact wrench comprised by a first arm, a crank eccentrically positioned on one side of said arm, a shaft concentrically positioned on the other side of said arm, a sector shaped hammer head mounted on the outer end of said arm, a hub adapted to receive a wrench socket at one end concentrically positioned with respect to said shaft, a free running connection between said shaft and said hub, a second arm on said hub, and a sector shaped anvil member mounted on the outer end of said latter arm having its top aligned in the same cylindrical surface with the top of said hammer head, and being positioned in alignment with the hammer head transversely of the axis of the shaft and the hub.

6. An impact wrench comprised by a first pair of oppositely disposed arms, a crank eccentrically positioned on one of said arms, on one side of the latter, sector shaped hammer heads mounted on the outer ends of said arms, a shaft concentrically positioned on the other side of said arms, a hub adapted to receive a wrench socket at one end concentrically positioned with respect to said shaft, a free running connection between said shaft and said hub, 21 second pair of oppositely disposed arms on said hub, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of said hammer heads, and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shank and the shaft.

7. An impact wrench comprised by a first pair of oppositely disposed arms, a crank concentrically positioned on one of said arms, on one side of the latter, sector shaped hammer heads mounted on the outer ends of said arms, a shaft concentrically positioned on the other side of said arms, a hub having an axial bore through part of its length rotatably receiving said shaft and adapted to receive a wrench socket at one end, a second pair of ppositely disposed arms on said hub, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of the hammer heads and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shaft and the hub.

8. An impact wrench comprised by a first pair of oppositely disposed arms, a crank eccentrically positioned on one of said arms and on one side of the latter, sector shaped hammer heads mounted on the outer ends of said arms, a shaft concentrically positioned on the other side of said arms and having an annular groove therein adjacent its end, a hub having an axial bore through part of its length rotatably receiving said shaft and adapted to receive a wrench socket at one end, a set screw extending through the wall of the shank and received in the annular groove in the shaft, a second pair of oppositely disposed arms on said hub, and sector shaped anvil members mounted on the outer ends of said latter arms having their tops aligned in the same cylindrical surface with the tops of said hammer heads, and being positioned intermediate the hammer heads and aligned with the latter transversely of the axis of the shaft and the hub.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,521 Pierce July 1, 1941 2,257,089 Caminez Sept. 30, 1941 2,282,743 Pervier May 12, 1942 2,600,796 Nash June 17, 1952 FOREIGN PATENTS 280,510 Great Britain Jan. 12, 1928 662,486 Great Britain Dec. 5, 1951 

1. AN IMPACT WRENCH COMPRISED BY A FIRST ROTATABLE MEMBER, A CRANK ON SAID FIRST ROTATABLE MEMBER, A SECOND CONCENTRICALLY POSITIONED ROTATABLE MEMBER ADAPTED TO RECEIVE A WRENCH SOCKET, A FREE RUNNING CONNECTION BETWEEN SAID ROTATABLE MEMBERS, A FIRST PAIR OF ARMS ON SAID FIRST ROTATABLE MEMBER, SECTOR SHAPED HAMMER HEADS MOUNTED ON THE OUTER ENDS OF SAID ARMS, A SECOND PAIR OF ARMS ON SAID SECOND ROTATABLE MEMBER, AND SECTOR SHAPED ANVIL MEMBERS MOUNTED ON THE OUTER ENDS OF SAID LATTER ARMS HAVING THEIR TOPS ALIGNED IN THE SAME CYLINDRICAL SURFACE WITH THE TOPS OF SAID HAMMER HEADS, AND BEING POSITIONED INTERMEDIATE THE HAMMER HEADS AND ALSO ALIGNED WITH THE LATER TRANSVERSELY OF THE AXIS OF SAID ROTATABLE MEMBERS. 